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post #1 of 4 Old 10-03-2018 Thread Starter
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Replaced Autoprop with Flexofold

Here's an update on replacing our 11 year old 3 blade feathering autoprop with a new folding Flexofold 3 blade:

Noticed some vibration so dove the boat at Santa Cruz island off Santa Barbara. Sure enough one of the blades on the autoprop was loose as if the bearing was going. Had to do something before trekking up the coast so decided to replace instead of repair. Don't think it was ever the right prop for out boat. Decided to go with flexofold versus maxprop. Flexofold was much less money (by 1/3), does not need to be greased, and has gotten some pretty good reviews and I wanted to try out a folding prop. Both look like great props. Headed back to Santa Barbara to get it done. Nice place to be stuck!

Prop arrived from Denmark in two days as promised. I took it out and dry fit it on the floor to make sure all the parts were there. I was very impressed at how well it fit together and the simplicity. Clearly a well designed and fabricated piece of gear. It was all set up with thread loc for installing/assembling under water so we found a diver (Salty Dog Diving) in Santa Barbara to install. Those guys were great to work with and I highly recommend them. They took off the old prop and installed the new in no time and then checked it after we did a sea trial. Saved time and money and stress on the boat versus pulling in a yard. So far we've put about 50 hours on it cruising from Santa Barbara to the Channel Islands and then motoring, motor sailing, and sailing ~300NM up the coast to San Francisco Bay. All sorts of conditions. Here are my impressions so far:

1) motoring moves the boat at least as well as the autoprop. 5knt easily at a lazy 2100rpm, 6.8knt max throttle (clean 37' double ended hull)
2) much smoother going into gear and running. Used to klunk going into gear and now harly notice it. Used to be rpm sweet spots now every rpm is smooth.

3) reverse is fine. I may give it a little more throttle but it is strong.
4) a little less prop walk in reverse but still there. It might be a little more user friendly now.
5) no longer have to keep the tranny in gear while sailing although do hit reverse with engine off to fold it most of the time.
6) I think the boat moves better in light air but that might be my imagination and wishful thinking.
7) rpm still max's at 2900 (rpm in neutral 3600) as did the autoprop. Flexofold double checked their calculations and say the pitch checks out. not sure what to make of this.
8) "grinding" into 15-20kn wind and swells is still "grinding". need a magic carpet to make that better I think.

In summary and very happy so far. I'll tune up the autoprop and put it up for sale.
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Last edited by dadio917; 10-03-2018 at 05:09 PM.
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post #2 of 4 Old 10-03-2018
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Re: Replaced Autoprop with Flexofold

Really nice to purchase something and have it live up to expectations.
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post #3 of 4 Old 10-04-2018
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Re: Replaced Autoprop with Flexofold

Very glad to hear you're pleased with the purchase. These are pricey items, even if less than a competitor, so I understand the anxiety. I have just a couple of things to consider, from your rundown.

I'm pretty sure the FOF literature says you don't need to grease them, but they work better if you do.

I don't understand why one would need to put a folding prop in reverse to get it to fold. That's usually necessary for a feathering prop, as the blades in forward pitch will windmill. Reverse causes them to feather, then you return the gear to neutral.

RPM in neutral is not a thing and is always different from under load. Your engine is rated for a max RPM, under load, and that's what it should make at wide open throttle. Look it up, if you're not sure what it's supposed to be. If it doesn't, it's usually prop pitch, but can be other factors too. Engine tachometers are notoriously out of calibration. A cheap $20 laser tach can confirm WOT rpm. Anything less than 100 rpm away from what says it's rated for should be fine.

Not sure what you mean by grinding, but it sounds more like the transmission than the prop. Motoring into waves can cause sudden decreases in speed, when the oncoming wave face pushes back. That can be very hard on a transmission. In those circumstances, it's best to either power down (the gear has more cushion to max tolerance, at lower horsepower input) or change your heading to reduce the affect.

Enjoy the new prop and the cruising!!

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post #4 of 4 Old 10-04-2018
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Re: Replaced Autoprop with Flexofold

Originally Posted by Minnewaska View Post

I don't understand why one would need to put a folding prop in reverse to get it to fold. That's usually necessary for a feathering prop, as the blades in forward pitch will windmill. Reverse causes them to feather, then you return the gear to neutral.
I have a Martec folder. It will windmill when I put the trans in neutral and shut the engine down once the sails are up I am sailing. It is necessary to shift the trans into gear for a moment to stop the shaft from spinning and close the prop.

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